Time register arrangement for air compressors



June 21, 1966 N. R. SIEWERT 3,256,685

TIME REGISTER ARRANGEMENT FOR AIR COMPRESSORS Filed Jan. 5, 1962 2Sheets-Sheet 1 JNVENTOR. FIG. 2 NORMAN R SIEWERT Atfamy N. R. SIEWERTJune 21 1966 TIME REGISTER ARRANGEMENT FOR AIR COMPRESSORS 2Sheets-Sheet 2 Filed Jan. 5, 1962 INVENTOR. NORMAN R. SIEWERT UnitedStates Patent O 3,256,685 TIME REGISTER ARRANGEMENT FOR AIR COMPRESSORSNorman R. Siewert, Rochester, N.Y., assignor to Siewert EquipmentCompany, Inc., Rochester, N.Y., a corporation of New York Filed Jan. 5,1962, Ser. No. 164,516 4 Claims. (Cl. 58--145) This invention relates toair compressors, and more particularly to means for recording therespective periods of time during which a compressor, or a series ofcompressors, operates to produce a given output pressure.

Today, there are many industries which rely upon compressed air foroperating machines. One problem always is maintenance. In thedry-cleaning and laundry businesses, for example, one of the problems istimely anticipation of the need for checking and/or overhaul of thecompression equipment. To properly anticipate this need and to thusavoid shutdowns, it is desirable to be able to ascertain readily at anytime the number of hours at which a respective compressor has beenoperating, and more particularly, the number of hours during which ithas been operating at various stages between zero and full capacity.When such information is not available, compressors are often permittedto operate for extended periods of time without receiving propermaintenance. I

A primary object of this invention is to provide means for recordingaccurately the total time of operation of a compressor.

Another object of this invention is to provide means for determining thetime during which a compressoroperates at various loads between zero andfull load.

A further object of this invention is to provide a means which is easilyinstallable in an existing compressed air system for recording bothtotal operating time and operating times at different loads of acompressor.

Other objects and features of the invention will be apparent from thefollowing specification and the appended claims, particularly when readin conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a diagram illustrating a recorder made according to oneembodiment of this invention and showing how this novel recording devicemay be inserted in a compressed air system;

FIG. 2 is a schematic view illustrating structure and wiring of thenovel recording device, the portion at the left of the figure being arear view of the front panel of the device and the portion at the rightof the figure being a front view of the rear panel or cover of thedevice, the pressure switch of the device being cut away in part; and

FIG. 3 is a similar schematic view of a further embodi ment of theinvention, the portion at the left being a rear view of the front panelof this recording device and the portion at the right being a front viewof the rear cover or enclosure of the device.

Referring now to the drawings by numerals of reference, and first to theembodiment of the invention shown in FIGS. 1 and 2, 10 denotes aconventional air compressor, and 12 a motor for operating the samethrough a standard belt and pulley drive 13. Operation of motor 12 iscontrolled by a manually-operable conventional disconnecting switch 14which may be closed to energize starter 16 for the motor. Air for thecompressor is sucked through a conventional filter 20 and deliveredthrough piping 22 to the intake side of the compressor. Air compressedby the compressor 10 is carried unidirectionally through the compressedair discharge pipe line 21 to a receiver or system reservoir 28, fromwhence it may pass through pipe 29 to the various machines or deviceswhich are to' be operated by the compressed air.

The invention is particularly adaptable to a compressor of the typewhich employs conventional Free-Air Unloaders on each of the one or moreinlet valves of the compressor. These unloaders are adapted to :becontrolled in conventional manner by means of an auxiliary valveinterposed between the unloaders and the compressed air reservoir. InFIG. 1, for example, one side of an adjustable auxiliary valve 25 isconnected by means of pipe 27 to the reservoir 28, whereby said one sideis always subjected to the system pressure. The other side a valve 25 isconnected by means of pipe 24 to the one or more Free-Air Unloaders (notillustrated) on the compressor inlet valve or valves (not illustrated)that communicate with the air inlet pipe 22. Auxiliary valve 25 may beadjusted so that at a predetermined pressure of the air in reservoir 28,(usually the desired maximum system pressure) valve 25 will open toadmit air from receiver 28 to pipe 24 and the Free-Air Unloaders. Whenthe unloaders are thus placed under system pressure, they maintain thecompressor air inlet valve or valves in open positions so that air isfree to pass in and out of the valves without being compressed. In suchinstance the compressor runs -free-i.e., its piston continues toreciprocate but without compressing air. On the other hand, when the airpressure in reservoir 28 drops below the predetermined value, auxiliaryvalve 25 closes (such valves normally being loaded by an adjustablespring) to simultaneously close ofi reservoir 28 from the unloaders sothat the unloaders permit the compressor inlet valves to function innormal manner. Assuming the system is designed for a maximum pressure of100 pounds per square inch, auxiliary valve 25 is adjusted so that itopens when the air pressure in receiver 28 reaches 100 pounds per squareinch. When valve 25 opens compressor 10 continues to run but. does notcompress air. When the air pressure in reservoir 28 drops below 100pounds per square inch the valve 25 closes, thereby relieving thepressure on the unloaders. Compressor 10 then begins once again tocompress air thereby to raise the system pressure back to 100 pounds persquare inch. The system thus far-described is conventional. v

The recorder or totalizer of the present invention is designatedgenerally at 30. It is connected to the line 24 by means of piping 32and to the electrical starter 16 by the electrical conductors or wires34, 35. The totalizer or recording device 30 includes two time clocks 38and 39, and a pressure switch 40. Time clock 38 records the number ofhours during which the compressor is running under load (periods duringwhich the compressor is actually compressing air) and time clock or hourmeter 39 records the total number of hours during which the compressoris operating, whether under load or when running free.

Wire leads 34 and 35 from starter 16 are connected to the lower side ofterminal block 44 (FIG. 2) of the recorder at terminals 45 and 46,respectively. Through a wire jump in the block, terminal 45 (hence, wire34) is connected to wire 47 which in turn is connected at 48 to oneterminal of the electric motor for time clock 39. The other terminal 49of this motor is connected by wire 50 to block 44, from whence it isconnected by a wire jump to terminal 46 and to the other lead 35 fromstarter 16. Hence, whenever the motor 12 is running time clock or hourmeter 39 will run, and will thus record the total operating time ofcompressor 10.

One terminal 52 of the motor which actuates time clock 38 is permanentlyconnected through wire 53 to terminal 48 of the motor which actuatestime clock 39.

The other terminal 54'of the motor for time clock 38 is connected bywire 55, terminal 56 of block 44, and wire 57 to terminal 58 of pressureswitch 40. This switch includes a leaf spring blade 60 and relativelyfixed off and on terminals 61 and 62, respectively.

The pressure switch 40, as previously described, is connected by line 32.to line 24. Line 32 supplies compressed. air from receiver 28 to oneside of a flexible diaphragm 63, or a piston, bellows, Bourdon tube orother pressure sensitive device, whenever auxiliary valve 25 is open.This diaphragm carries a plunger 64 which engages the switch blade 60.When valve 25 opens, as the system reaches its maximum pressure,diaphragm 63 is subjected to system pressure so that plunger 61 movesand holds blade 60 in contact with terminal 61 which is dead-ended as at67, thereby preventing the operation of clock 38. However, when thesystem pressure falls below a predetermined maximum, valve 25 closes andexhausts line 32 to the atmosphere so that the pressure in diaphragm 63is decreased, thus permitting plunger 64 and the free end of springswitch blade 60 to move downwardly in the direction in which it isnormally urged, to make contact with terminal 62 of pressure switch 40.Terminal 62 is connected by the wire or lead 66 and a jumper wire of theblock 44 to line 35. Hence when blade 60 engages terminal 63 a circuitwill be closed to clock 38 from line 34 through terminal 48 of clock 39,line 53, terminals 52 and 54, the motor of the time clock 38, line 55,terminal 56 of block 44, line 57, blade 60, terminal 62 of pressureswitch 40, line 66, and block 44, to line 35. Thus time clock 38 willrun as long as there is no system pressure on diaphragm 63 (auxiliaryvalve 25 closed), or in other words, as long as the system pressure isbelow a predetermined maximum and the compressor is under load andactually compressing air to elevate the system pressure once again toits predetermined maximum. The clock or hour meter 38 thus affords apermanent count or visual record of the time during which the compressor10 is loaded (actually compressing air rather than running free), andhour meter 39 affords a record of the total time during which compressor10 is running (under load or otherwise) FIG. 3 illustrates a furtherembodiment of the invention employing time clocks and pressure switchesto record the total running time of the compressor and the individualrunning time of the compressor at various stages of its operation. Byway of example, assuming a maximum system pressure of 100 pounds persquare inch, four of the clocks will be employed to measure,respectively, the times during which the compressor is operating toelevate the system air pressure or the air pressure in receiver 28 to 94pounds per square inch, from 94 pounds per square inch to 96 pounds persquare inch, from 96 pounds per square inch to 98 pounds per squareinch, and from 98 pounds per square inch to 1 pounds per square inch,respectively. Such operating times are analogous to operation of thecompressor at full load, three-quarter, one-half, and one-quarter fullload, respectively.

In FIG. 3, 30 denotes the recording unit or totalizer as a whole. Thisunit includes a plurality of time clocks 70, 71, 72, 73 and 74 forindicating, respectively, the total time of operation of the compressor(both running free and loaded) and the times of its operation underfull, three-quarter, half, and one-quarter load. As in FIG. 2, the wireleads 34, 35 from starter 16 are connected to one side of a terminalblock 44 and are jumped by wires to terminals 75 and'76, respectively,at the opposite side of the block. Compressed air is delivered from thesystem receiver, through four auxiliary valves (not illustrated) similarto the type described at 25 in FIG. 1, and into totalizer 30 by pipes77, 78, 79 and 80. These pipes deliver the compressed air against thediaphragms of pressure switches 82, 83, 84 and 85, respectively. Each ofthese switches has a diaphragm operated switch blade 60 and is similarto pressure switch 40 illustrated in FIG. 1. However, while theauxiliary valve associated with switch 85 is adjusted for a maximumsystem pressure of say 100 pounds per square inch, the auxiliary valvesassociated with switches 84, 83 and 82 are set or adjusted to close(thereby permitting the corresponding spring switch blade 60 to drop toits lower position) when the receiver or system pressure drops below say98 pounds per square inch, say 96 pounds per square inch and say 94pounds per square inch, respectively.

The time clock 70 records the total running time of the compressor 10,and hence is not associated with a pressure switch. Instead, this timeclock is continuously in circuit with the motor through wire lead 34,block 44',

wire 86, one terminal 87 of the motor for time clock 74,

wire 88, one terminal 89 of the motor of clock 73, wire 90, one terminal91 of the motor for time clock 70, through the motor to the oppositeterminal 92 thereof, and back through wire 93 to terminal 76 of block44', and through a wire jump to wire 35 to starter 16.

While clock 70 is continuously in circuit with motor 12, the motors forthe remaining time clocks 71 to 74 are in circuit with starter 16 onlyupon the moving of their respective pressure switch blades 60 downwardlyas their corresponding auxiliary valves close and exhaust pipes 77, 78,79 or 80 to the atmosphere. FIG. 3 is illustrative of the positionsassumed by the pressure switch blades 60 (all up) when the receiver orsystem is under the maximum pressure of 100 pounds per square inch. Atthis time, one terminal for the motors in each of clocks 70 to 74 isconnected, and remains connected, to starter 16 as shown by wire 34which is connected through block 44' to wire 86, terminal 87 of themotor for clock 74, wire 88, terminal 89 for the motor in clock 73, wire90, terminal 91 for the motor in clock 70, wire 94, terminal 95 for themotor in clock 71, and wire 96 to terminal 97 for the motor in clock 72.However, an open switch (described below) is interposed between each ofthe remaining terminals 98-, 99, 100 and 101 of the motor for clocks 74,73, 72 and 71, respectively, whereby the latter four clocks are notrunning when the system is at 100 pounds per square inch. Instead,terminal 98 is connected through wire 103, terminal block 106, and wire107 to the switch blade 60 in pressure switch 85, which blade is inengagement with the upper pressure switch terminal (comparable toterminal 61 in pressure switch 40). In pressure switch 85 the last-namedupper terminal is dead-ended as at 67' so that the circuit between themotor terminal 98 in clock 74 and wire lead 35 to starter 16 isinterrupted, thereby preventing the operation of clock 74. Similarly,the circuit between the motor termi nal 99 for clock 73 and the wire 35leading from starter 16 is interrupted since terminal 99 is connected bywire 104, block 106, and wire 108 to the lower terminal in pressureswitch 84 (comparable to terminal 62 in pressure switch 40), which lowerterminal is elfectively dead-ended when the system is at maximumpressure because the switch blade 60 in pressure gauge 84 is inengagement with the upper terminal of switch 84 at such time. Thus clock73 is not running. Nor is clock 72 running at this time either since itterminal 100 at this time is connected by wire through clock 106 to wire109 and to the lower terminal of pressure switch 83, and switch blade 60in switch 83 is out of contact with this lower terminal when the systemis at maximum pressure. Likewise clock 71 is not running at this timesince its motor terminal 101 is connected through wire 111, terminal 112on block 44, and wire 113 to the lower terminal of pressure switch 82which is out of engagement with switch blade 60 of switch 82 when thesystem is at maximum pressure.

However, when system pressure drops below 100 pounds per square inch,but remains above 48 pounds per square inch, switch blades 60 ofswitches 82 to 84 remain up, but blade 60 of switch 85 descends intoengagement with the lower terminal of this switch 85 to thereby completethe circuit between the motor terminal 98 of clock 74 and starter 16 bymeans of wire 103, block 106, wire 107, switch blade 60 of pressureswitch 85, the lower terminal of switch 85, wire 114, wire 115, theupper terminal' and switch blade 60 of pressure switch 84, wire 116,wire 117, the upper terminal and switch blade 60 of pressure switch 83,wire 118, wire 119, the upper terminal and switch blade 60 Olf pressureswitch 82, wire 120, terminal 76 on block 44, and wire 35 to starter 16.

As the system pressure drops below 98 pounds per .square inch butremains above 96 pounds per square inch switch blade 60 of pressureswitch 84 becomes disengaged from the upper terminal of switch 84, anddrops to engage the lower terminal of switch 84 to complete the circuitfrom motor terminal 99 of clock 73 through wire 104, block 106, wire108, lower terminal and blade 60 of pressure switch 84, wires 116 and117, the upper terminal and blade 60 of switch 83, wires 118 and 119,the upper terminal'and blade 60 of the switch 82, wire 120, terminal 76of block 44', and wire 35 to starter 16. Clock 74 is thus stopped, andclock 73 is started.

As the system \pressure falls below 96 pounds per square inch butremains above 94 pounds per square inch, switch blade 60 of pressureswitch 83 drops, thereby interrupting the circuit for the motor in clock73 and completing the circuit for motor terminal 100 of'clock 72 throughwire 105, block 106, wire 109, the lower terminal and blade 60 ofpressure switch 83, wires 118 and 119, the upper terminal and blade 60of pressure switch 82, wire 120, terminal 76 on block 44', and wire ;.35to starter 16. Clock 73 is thus stopped, and clock 72 is started.

,For system pressures below 94 pounds per square inch the switch blade60 of pressure switch 82 drops from the upper tothe lower terminal ofthis pressure switch thereby interrupting the motor circuit for clock 72and completing-the circuit from motor terminal 101 of clock 71 throughwire 111, terminal 112 on block 44, Wire 113, the'lower terminal andblade 60 of switch 82, wire 120, and terminal 76 on block 44', and wire35 to starter 16. Clock 72 is thus stopped and clock 71 is started.

From the foregoing it will be apparent that the four clocks 74, 73, 72and 71 record the respective times during which the compressor isoperating (actually compressing air in the system) against a system ordischarge pressure of say from 98 to 100 pounds per square inch, 96 to98 pounds per square inch, 94 to 96 pounds per square inch, and tfrombelow and up to 94 pounds per square inch (gauge), respectively.

While the devices have been described in terms of decreasing airpressure in the system, it is apparent that as the pressure in thesystem increases from below- 94 to maximum (100 pounds per square inch)each of the hour meters 71, 72, 73 and 74 will be successively energizedand then deenergized as the increasing pressure of the systemsuccessively opens their corresponding auxiliary valves. E.g., as systempressure increases beyond say 94 pounds per square inch, blade 60 ofswitch 82 is moved from the lower to the upper terminal of switch 82,thereby interrupting the motor circuit for hourmeter 71, and completingthe circuit for the motor in hourmeter 72. This action does not startclocks 73 and 74 because the blade 60 in switch 83 is down, until systempressure exceeds 96 pounds per square inch.

Moreover, although the system illustrated in FIG. 3 is set to recordquarterly stages of compressor operation, it is apparent that theinvention will serve to record various fractional stages of compressiondepending upon the number of hourmeters and pressureswitches employed,and the manner in which their corresponding auxiliary valves areadjusted. For instance, in measuring three stage compression, thepressure switches and auxiliary valves may be connected to correspondinghourmeters, .the auxiliary valves being adjusted to operate at zero,onehalf and maximum compressor load, respectively. Moreover, althoughthe invention has been described as utiliz- 6 ing auxiliary valves tocontrol the operations of the various pressure switches, therebyaffording a more instantaneous opening and closing of the switch blades60 with the terminals in the various pressure switches, it is possibleto eliminate the auxiliary valve and connect the pressure switchesdirectly to .the receiver. In such instance the pressure switches willconstantly be in communication with and responsive to the receiverpressure. When so connected and used to electrically energize andde-energize a three-way solenoid valve simultaneously with itsrespective time clock, the pressure switch acting in conjunction withthe solenoid valve will replace the function of the auxiliary valve.Therefore, the various pressure switches will have to be of theconventional type which can be individually adjusted, or which areotherwise designed so that their respective spring blades 60 will bemoved into engagement with the upper terminal of the respective pressureswitch only when the diaphragm in the switch has been subjected to apredetermined system pressure.

While the invention has been described in connection with a specificembodiment thereof, it will be understood that it is capable of furthermodification, and this application is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent disclosure as come within known or customary practice in the art.to which the invention pertains and as may be applied to'the essentialfeatures hereinbefore set forth, and as fall within the scope of theinvention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. The combination with (a) an air compressor, (b) an electrical motorfor operating said compressor to supply air under pressure to areservoir, (c) a valve-controlled air inlet foradmitting air to thecompressor, ((1) a reservoir connected to the compressor for storing thecompressed air, and (e) a valve connected to said reservoir to be openedwhen the pressure in said reservoir reaches a predetermined value, saidvalve, when open, permitting flow of the compressed air from thereservoir to said inlet so that air is free to pass in and out of thecompressor without being compressed, (f) of apparatus for recording theduration of compressor operation at various stages of loading, saidapparatus comprising (g) aplurality of time clocks,

(h) a circuit including a plurality of switches for selectivelyconnecting said clocks respectively in parallel circuit with saidmotorfor operation therewith, each of said switches being interposed,respectively, in a circuit associated with one of said clocks,

(i) a plurality of pressure responsive elements for op- (1) meansoperative upon connection of one of said clocks .to disconnect the otherclocks.

2. The combination with (a) an air compressor,

(b) an electric motor for driving the compressor,

(c) a valve-controlled air inlet for admitting air to the compressor,

(d) a reservoir connected to the compressor for storing compressed air,and

(e) a valve connected to said reservoir to be opened when the pressurein said reservoir exceeds a pre- 7 determined value, said valve, whenopen, permitting flow of the compressed air from the reservoir to saidinlet so that air is free to pass in and out of the compressor withoutbeing compressed, (f) of a plurality of electrically-operated timeclocks, (g) means continuously connecting a first clock in parallelcircuit with said motor to operate when said motor operates, thereby torecord the total operating time of said compressor,

(h) means including a pressure-operated switch movable from a firstposition .to a second position for connecting and disconnecting,respectively, a second time clock into and out of parallel circuit withsaid motor, and

(i) means conecting said switch to said valve so that when said valve isopen said switch is moved to its second position to disconnect saidsecond time clock from the circuit and when said valve closes saidswitch moves to its first position to connect said second time clock incircuit to record the runing time of the compressor under load.

3. The combination with (a) an air compressor,

(b) an electric motor for driving the compressor,

(c) a valve-controlled air inlet for admitting air to the compressor,

(d) a reservoir connected to the compressor for storing compressed air,and

(e) valve means connected to said reservoir to be opened when thepressure in said reservoir exceeds a predetermined value, said valvemeans, when open, permitting flow of the compressed air from saidreservoir to said inlet so that air is free to pass in and out of saidreservoir without being compressed,

(f) of more than two time clocks,

(g) a separate-pressure operated switch associated with each time clock,each pressure operated switch being movable from a first position to asecond position for connecting and disconnecting, respectively, theassociated time clock into and out of parallel circuit, respectively,with said motor, the separate switches being connected to said reservoirand being adapted, respectively, to be held in their respective secondpositions when said reservoir is at respectively diflferent pressures,each switch being constructed to move to its respective first positiononly when the pressure in said reservoir drops below said predeterminedvalue to a respective given pressure which is different for each switch,whereby at a given time only those switches will be in their respectivefirst positions, to which the pressure applied is insufficient to holdthem in their respective second positions, said switches being soconnected together electrically that only that switch, which is in itsfirst position and moves to such first position at the lowest givenpressure then prevailing in the reservoir will close a circuit to itsassociated time clock, whereby only one of the time clocks associatedwith said switches will be in circuit at a time, thereby to record thetime of operation of the compressor at the pressure at which therespective associated switch is in its first position.

4. A combination as claimed in claim 3, wherein (a) an additional timeclock is provided, and

(b) means is provided continuously connecting said additional time clockin parallel circuit with said m0- tor to operate when said motoroperates, thereby to record the total operating time of the compressor.

References Cited by the Examiner UNITED STATES PATENTS 1,340,324 5/1920Buck 58-146 1,414,910 5/1922 Watson 58-146 X 1,475,831 11/1923 Johnsonet al 58-147 1,566,290 12/ 1925 Swift 58-395 2,501,960 3/1950 Olson58-39.5 X 2,679,038 5/1954 Cross et a1. 58- X LEO SMILOW, PrimaryExaminer.

H. R. MOSELEY, Examiner. C. I. BORUM, G. F. BAKER, Assistant Examiners,

1. THE COMBINATION WITH (A) AN AIR COMPRESSOR, (B) AN ELECTRICAL MOTORFOR OPERATING SAID COMPRESSOR TO SUPPLY AIR UNDER PRESSURE TO ARESERVOIR, (C) A VALVE-CONTROLLED AIR INLET FOR ADMITTING AIR TO THECOMPRESSOR, (D) A RESERVOIR CONNECTED TO THE THE COMPRESSOR FOR STORINGTHE COMPRESSED AIR, AND (E) A VALVE CONNECTED TO SAID RESERVOIR TO BEOPENED WHEN THE PRESSURE IN SAID RESERVOIR REACHES A PREDETERMINEDVALUE, SAID VALVE, WHEN OPEN, PERMITTING FLOW OF THE COMPRESSED AIR FROMTHE RESERVOIR TO SAID INLET SO THAT AIR IS FREE TO PASS IN AND OUT OFTHE COMPRESSOR WITHOUT BEING COMPRESSED, (F) OF APPARATUS FOR RECORDINGTHE DURATION OF COMPRESSOR OPERATION AT VARIOUS STAGES OF LOADING, SAIDAPPARATUS COMPRISING (G) A PLURALITY OF TIME CLOCKS, (H) A CIRCUITINCLUDING A PLURALITY OF SWITCHES FOR SELECTIVELY CONNECTING SAID CLOCKSRESPECTIVELY IN PARALLEL CIRCUIT WITH SAID MOTOR FOR OPERATIONTHEREWITH, EACH OF SAID SWITCHES BEING INTERPOSED, RESPECTIVELY, IN ACIRCUIT ASSOCIATED WITH ONE OF SAID CLOCKS, (I) A PLURALITY OF PRESSURERESPONSIVE ELEMENTS FOR OPERATING SAID SWITCHES, EACH OF SAID ELEMENTSBEING INTERPOSED BETWEEN SAID RESERVOIR AND ONE OF SAID SWITCHES, (J)SAID ELEMENTS BEING CONNECTED TO SAID RESERVOIR AND BEING OPERATIVE WHENTHERE IS A PREDETERMINED PRESSURE IN SAID RESERVOIR TO CAUSES SAIDSWITCHES TO DISCONNECT ALL SAID CLOCKS FROM SAID MOTOR, (K) EACH OF SAIDELEMENTS BEING OPERATIVE AT RESPECTIVELY DIFFERENT PRESSURES BELOW SAIDPREDETERMINED PRESSURE TO CAUSE THE RESPECTIVE CORRESPONDING SWITCH TOCONNECT THE CLOCK ASSOCIATED THEREWITH IN CIRCUIT WITH SAID MOTOR, AND(L) MEANS OPERATIVE UPON CONNECTION OF ONE OF SAID CLOCKS TO DISCONNECTTHE OTHER CLOCKS.